Ed Grochowski's Website
Electronic Project Museum
Stereo 3 Amplifier
Stereo 4 Amplifier
Phono Preamplifier
Genius 2 Computer
Regulated Power Supply
Audio Signal Generator
Ocean Sound Synthesizer
Home Security System

Genius 2 Computer


I have spent more time on this project than all other projects combined. As the name implies, the Genius 2 was the second computer I have designed and built. The first was a Z80 machine built in 1978. The Genius 2 computer was designed and built in 1983 and served me well until 1995.

I learned a lot about logic design and programming from this machine. Although it uses LSI microprocessors and memory chips, many of its subsystems were designed with TTL. I wrote all the software for the Genius 2 myself. There is not a byte of commercial software on this computer. Most of the software on the software pages originated here.

The Genius 2 specifications are (keeping in mind this is an early 1980s computer):

  • 8 MHz 68000 processor
  • 5 MHz Z80B processor
  • 2 MBytes 41256 DRAM
  • 1 KByte 2708 EPROM
  • 1024 by 768 by 1 bpp bit-mapped graphics
  • 14" monochrome monitor (modified NEC JB1410)
  • 20 MByte hard disk (Seagate ST-225)
  • 600 KByte 8" floppy disk (NEC FD1165)
  • PC keyboard and mouse
  • Parallel printer port (for Epson MX-100 printer)
  • RS232 serial port (used by mouse)
  • Cassette tape interface
  • S-100 power supply with linear voltage regulators
  • Perf board and wire wrap construction
  • 350 integrated circuits (NMOS, LS-TTL, S-TTL)
  • TTL subsystems for memory, graphics, hard/floppy disk controllers
  • Software: total 110 K lines of code including operating system, editor, compiler, windows, and applications

December 1983Designed
Spring 1984 Running with 128KBytes memory
Spring 1985 Hard disk, serial port, and mouse added
August 1985 Memory upgraded to 2 MBytes
December 1990PC keyboard replaced original 8-bit parallel keyboard
Fall 1995 Decommissioned (i.e. put in the closet)
1995-2000 Software ported to PC
January 2004 Still works! PC mouse replaced original mouse
2011 Hard disk fails after a quarter century of service
December 2012Power supply capacitors replaced